170. Finding the God Particle

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Speaker 5 My guest today, Brian Cox, has had a very unconventional career trajectory. He started his adult life as a pop star, part of a band that had a number one hit on the British charts and did arena tours.

Speaker 5 Then he shifted gears and became a particle physicist, part of the team that discovered the Higgs boson. And for a third act in his career, he's back on tour and he is again selling out arenas.

Speaker 5 But this time, he's not playing music. Instead, he's giving science lectures.

Speaker 4 What is this thing we call science, this way of thinking and interrogating nature that's taken us from the end of the medieval period and onwards to the Enlightenment and then to the stars basically in 400 years.

Speaker 6 Welcome to People I Mostly Admire with Steve Levitt.

Speaker 5 We will certainly talk about Brian's multiple careers on stage, but I want to start with some particle physics.

Speaker 5 There was a media frenzy around the Higgs boson after the announcement of its discovery back in 2012.

Speaker 5 Honestly though, I've never had any idea why the Higgs boson matters to anyone, but I know it must be important because they call it the God particle.

Speaker 5 So I asked Brian to explain why it matters so much to physics to find the Higgs boson.

Speaker 4 The story goes back to the 1960s and the construction of our theory of subatomic particles and the way that they interact with each other, which is called the standard model of particle physics.

Speaker 4 So I can give you the the 30-second overview of that thing if you want.

Speaker 5 Please do, yeah.

Speaker 4 There are 12 fundamental matter particles. I use the word fundamental because as far as we can see, they don't have any structure.
They're point-like objects.

Speaker 4 So the electron would be the most familiar example. It's a thing that's just a single point.
You can't tell if it's got any size or not. There are also...

Speaker 4 Alongside the electron, the things that make up us and everything we see in the universe, there are two quarks called the up and the down quarks, and they make up protons and neutrons.

Speaker 4 And then there's one other particle called the electron neutrino, which is perhaps more unfamiliar but is intimately involved in nuclear reactions in the Sun.

Speaker 4 And there are many millions of them passing through your head every second and indeed passing through the whole Earth. They don't interact very strongly with anything at all.

Speaker 4 So four fundamental particles that you need to make up everything that we touch and indeed ourselves. There happen to be two copies of those four particles.

Speaker 4 So that's basically the standard model of particle physics. Those are the 12 matter particles.
And then there are three forces that we're concerned with in the subatomic world.

Speaker 4 There's electromagnetism, and then there's the strong nuclear force and the weak nuclear force. And just to be complete, electromagnetism is carried by photons.

Speaker 4 The weak force is carried by bosons called the W and Z bosons. And the strong force carried by gluons, which stick the nucleus together.

Speaker 5 I've always marveled at the names that have been given to these particles because some of them are super serious and some of them are almost like mocking.

Speaker 5 It was just up to the person who conjectured the particle to give it a name. Is that how it worked?

Speaker 4 Yeah, I mean the quarks, it was Mary Gellman who got the Nobel Prize for something called the Eightfold Way, which was essentially looking at all these particles that were springing up in the 1940s and 50s that we were discovering and looking for patterns in them.

Speaker 4 And the very famous quote from Finnegan's Wake called Three Quarks for Musta Mark or something like that, it was because he thought there were three of them at the time.

Speaker 4 And that explained the pattern we saw in the particles we were producing at particle accelerators. So he named that the gluon.

Speaker 4 It's a good name, the gluon, because it sticks quarks together in the nucleus. So it glues the nucleus together.
I think there's a bit of a randomness about it.

Speaker 4 It's because nobody really cares. You know, it's not like a planet or something where everybody cares about it.
You discover it or name it what you want, really.

Speaker 4 Essentially, we have a mathematical theory that describes how all that works that was really put together in the 60s and 70s and 80s, ultimately. So where does the Higgs fit in?

Speaker 4 It was realized in the 60s, and this is the really beautiful thing, that Obviously, things like an electron have a mass.

Speaker 4 And in particular, these things, the W and Z bosons that carry the weak nuclear force, they have a mass.

Speaker 4 And it was found that if you just put masses into the equation, then the whole thing essentially doesn't work. The theory doesn't function as it should.

Speaker 4 And so Peter Higgs and others in the 1960s discovered a way.

Speaker 4 to introduce masses into this equation that describes how all that works without breaking the we call them symmetries i spoke to Peter, not to name drop, but I did speak to him a few years ago.

Speaker 4 And I don't think that people thought it was really correct. It was interesting.
It was like, that's cool, that works.

Speaker 4 But it turns out that this way of introducing the masses predicts a particle associated with the mechanism for generating mass.

Speaker 4 And that particle is the Higgs boson.

Speaker 5 Okay, so just to understand, there's a whole set of equations that the standard model includes.

Speaker 5 And Higgs was just trying to figure out a mathematical fix, not at all concerned with reality, just trying to find a way on paper to make these equations all work out with math. Yeah.

Speaker 5 And then that predicts a particle. And amazingly, then people like you set out on a mini billion dollar quest to show that this thing that he made up might actually exist.

Speaker 4 Yeah, because the standard model, again, talking to people who were around at the time in the 70s, 80s, I think it's often described as being far more successful than it had any right to be.

Speaker 4 This is how you do science. You guess theories.
Richard Feynman often pointed this out.

Speaker 4 You just guess a kind of a theory, a framework, and then you test the predictions against observation and experiment. I suppose in a way it was the first guess.
It was just there and it worked.

Speaker 4 And then, as you rightly say, 50 years later, you build a large hadron collider. We've been getting more and more confident that this thing may be there.

Speaker 4 As another aside, my most cited paper in my scientific career is called WW Scattering in the Absence of a Higgs boson. Okay.
It's the most cited paper, and it's wrong because there is a boson.

Speaker 4 And we were thinking about what physics would look like if there wasn't. It didn't have to be, that's the point.

Speaker 4 But people got more and more confident because the model, the theory, was making accurate predictions. And the more observations we made, we couldn't break this guess.

Speaker 4 So, what does it do, this thing, the Higgs? Basic idea is that particles get mass by interacting with the Higgs field. One way that it's often pictured is this kind of treacle or syrup.

Speaker 4 What's the US term?

Speaker 5 Maple syrup.

Speaker 4 Yeah, you can almost picture this stuff as filling the universe.

Speaker 4 And then particles that don't interact with it, so the photon, the particle of light would be an example, those particles do not acquire mass. And particles that do interact with it acquire mass.

Speaker 4 And the more they interact with it, the more massive they are. So that's essentially the idea.

Speaker 4 It was perhaps one of the examples of what the great physicist Wigner called the unreasonable effectiveness of mathematics in the physical sciences, because it was really mathematically motivated.

Speaker 4 But it turns out that it's correct. So there is this thing.
called the Higgs field with this associated particle, the Higgs boson. We found it.

Speaker 4 And it's a different kind of particle to the other other particles that I've described but as we go on in physics and look at astrophysics for example it looks like there may be other examples of these things the Higgs is the one we have discovered and we're beginning to explore now but it looks like there may have been one of those things before the Big Bang that was responsible for something called inflation so that the simplest model is there is such a thing that makes the universe stretch very fast and that slowed down and the thing changed and that's what we call the big bang and then there are theories there's something called dark energy that we believe is present in the universe at the moment which is causing the rate of expansion of space to speed up and that was discovered in the 1990s although einstein had suggested it back in 1916 or 1917 that thing also could be one of these things so it's extremely interesting the higgs not only have we discovered it and it's good and it's the thing that gives mass to things like the W and Z bosons, but it's an example of something that we don't really understand in nature.

Speaker 4 And so that's why it is particularly interesting still, increasingly interesting, I would say, to explore how this thing actually behaves at a detailed level.

Speaker 5 So we've both been heaping praise on the theorists for being able to think this thing up before we found it.

Speaker 5 I think equally as impressive is the theorists, is the actual detection of something like the Higgs boson. And you were part of the team that found it back in 2012.

Speaker 5 Could you walk me through how one goes about demonstrating that this thing exists?

Speaker 4 Yeah, I mean, a particle physics detector is basically a big digital camera, really, but it's a very sophisticated one. And what it does is it detects particles.

Speaker 4 In this case, at the Large Hadron Collider, for example, we collide protons together. So we have this machine, which is 27 kilometers in circumference.
So what's that, 16 miles or so in circumference?

Speaker 4 We accelerate protons around there very fast to 99.999999% the speed of light.

Speaker 5 Why do you collide protons instead of hydrogen atoms as a whole?

Speaker 4 Oh, well, because protons are the nuclei of hydrogen atoms, but they're electrically charged. They don't have the electron.
And that's important because that's how we bend them around the circle.

Speaker 4 because it's basically magnets. So you have a load of magnets and this is a charged particle.

Speaker 4 So it goes around so you can control it you couldn't even accelerate an atom i see okay so the charge is the key thing because that's interacting with the electric fields and the magnets basically anything that's charged you can send around but we do it with protons when we're doing particle physics it's just a way of delivering energy really so for the purposes of discovering things like the higgs particle you don't care what you collide what you care about is how much energy you can get into the collision into a small space because as einstein told us equals mc squared So if you get a lot of energy in a small space, you can make heavier things or more massive things.

Speaker 4 So really, the basic point is you want to collide these things together and produce for a very short space of time, something like a Higgs boson.

Speaker 5 Okay, so let me ask you a really dumb question. So I understand how you're getting these things to go really fast through electric charges and magnets.

Speaker 5 How do you get one proton to go in one direction and the other one to go in the opposite direction?

Speaker 4 Oh, well, it's very clever. The easiest way to do it is to use one beam of anti-protons, right?

Speaker 4 So the Tevatron collider near Chicago, where I also worked at Fermilab, was a proton-anti-proton collider.

Speaker 4 So the thing is, because they're identical, so an anti-metaproton is identical to a proton, except it's got the opposite charge. It's got a negative charge rather than positive.

Speaker 4 So that means you can send one lot around one way and the other lot around the other way, and they bend in the opposite direction, basically.

Speaker 4 There is a disadvantage to that, which is that, see, protons are easy to get because they're just hydrogen. So you just get some hydrogen gas and heat it up basically and strip the electrons off.

Speaker 4 Antiprotons, you've got to make them in collisions. And so if you want to collide lots of particles together, it's better to just use protons because they're easier.

Speaker 4 But you need a much more complex magnet setup.

Speaker 4 So the LHC is a proton collider, but the magnets are complicated so that, as you said, one beam can go one way and the other beam can go the other way and so that's how it works so to your question then what happens then so you smash the protons together you make a big mess when you smash protons together because there's loads of stuff inside protons gluons and quarks and so most of the time you just get a big mess but sometimes because particle physics is statistical, it's quantum mechanics, occasionally you get something interesting.

Speaker 4 And very occasionally, you'll get a Higgs particle.

Speaker 5 And just to be clear, the Higgs particle is not inside of the protons. The Higgs particle is somehow a result of this incredibly high intensity crash.
It's very different than it breaking into pieces.

Speaker 5 Yeah. Yeah.
Is it turning energy into mass?

Speaker 4 Is that the way to think about it? Yeah, basically the energy in the collision can get converted into massive particles.

Speaker 5 And this is only happening because these things are going like virtually the speed of light, right?

Speaker 4 Oh, yeah. So 99.999999% the speed of light, just to give you some sense of how strange it is for things to go at that speed.

Speaker 4 So one of the consequences of relativity is that for things that are moving very fast relative to someone that's sat watching them fly by, time goes more slowly from the point of view of the person watching them whiz past.

Speaker 4 So moving clocks run slow, it's often described in relativity. So at that speed, the factor by which time slows down is 7,000.
Also, distances shrink, by the way.

Speaker 4 So from the point of view of the protons, the LHC circumference shrinks by a factor of 7,000. So it's no longer 27 kilometers.
It's four meters in circumference.

Speaker 4 It's what we call ultra-relativistic regime at those speeds. Very high energies.
So you can make heavy particles, essentially, massive particles. So what happens then?

Speaker 4 You're lucky in a particular collision, you happen to make a Higgs particle.

Speaker 5 Because just to be clear, like billions and billions of these protons are flying around like crazy.

Speaker 5 They hardly ever crash, but you're doing it long enough that you see billions of these crashes, and that's what you're trying to detect.

Speaker 4 Occasionally, of the billions of collisions that you make in a very short space of time, one or two of them are interesting.

Speaker 4 So one part of the art or the science or the engineering of particle physics is that you can't record the outcome of all those collisions. No way.
It's way too much data.

Speaker 4 So you have to pre-select interesting things and then just record those for further analysis. That's part of the trick, really.
But in any case, you make a Higgs boson. What happens to it?

Speaker 4 The general rule is that if something's very massive, then if it can fall to bits, it will fall to bits. We say it'll decay.
It exists for a fleeting moment. So you don't see the Higgs boson.

Speaker 4 What you see are the products of it falling to bits, the decay products of the thing. And there are different signatures you can look for.

Speaker 4 But what the particle physics detector does is to detect all the bits. There'll be things like protons and electrons and all sorts of things, all these fundamental particles.

Speaker 4 And essentially, you measure their path from the collision. You can reconstruct everything

Speaker 4 that happened from all these hundreds of particles flying out of the collision. And what you hope is that you see a signature that some heavy particle decayed.

Speaker 4 So it was made for a fleeting instant and then decayed into all these little bits. And you have to put all those bits together to find out what it was that happened.

Speaker 5 Now, does the theory tell you the different ways that the Higgs will reveal itself? Yeah. And that's where you look is where the theory tells you to look, essentially.

Speaker 4 And that's actually very important because the theory specifies many different ways that something like a Higgs boson can fall to bits.

Speaker 4 One of the most common ways is into two B quarks, the beauty quarks. So the Higgs boson can decay into a B quark and an anti-B quark, for example.

Speaker 4 And then those quarks turn into things called jets of particles, and you reconstruct those. So that's one way it can go.

Speaker 4 It could also go into a pair of what's called W bosons, a W plus and W minus, and then they go into something else with muons or electrons. So the theory has a prediction for how the Higgs behaves.

Speaker 4 In what percentage of collisions, when it's made, will it go to W bosons? In what percentage will it go to B quarks? And that's all about understanding the thing itself.

Speaker 4 So it's one thing discovering it, and it's a different thing trying to characterize it and trying to understand how it behaves.

Speaker 4 An analogy I often use, let's say we discover a new planet orbiting around the sun. You wouldn't say, oh, that's cool.
We've discovered it now. We'll stop.

Speaker 4 You'd want to go to the planet and you'd want to figure out what's on the planet and so on. That's why.

Speaker 4 it is extremely important to continue running the collider because not only are we looking for new things beyond the Higgs, but we're also really trying to find out exactly how this thing works.

Speaker 5 So you talked about your most cited paper. Was that an attempt to say if the Higgs boson doesn't exist and we smash these things together, what will we expect to see in a different world?

Speaker 4 Yeah.

Speaker 4 So, the reason that we knew that the Large Hadron Collider would certainly discover something was that the theory, the standard model, if you take the Higgs out of it, then the theory stops working.

Speaker 4 In particular, the collision of W boson. It predicted that the probability of these things colliding together was greater than one, which is complete nonsense.

Speaker 4 So you know that if you look at that process and there isn't a Higgs, nature puts something else in there.

Speaker 4 So it's a very powerful idea for an experimental physicist because you know that your theory breaks. So you had to discover something.
It was absolutely guaranteed.

Speaker 4 And so my paper was actually saying, well, how would we explore this process? Let's see how we can measure it. Whatever's there, let's see if we can find it.

Speaker 4 And the reason it was cited is because there were some techniques that we invented, which are widely used now to detect particles. But that was an aside.

Speaker 4 But I think it's kind of interesting because it shows you how science gets done.

Speaker 4 Because what you should do, or it's a good thing to do, is to say without any preconditions, let's look at this process, this thing that we can create in the laboratory, and let's observe it in the most general way and see what we can learn from it.

Speaker 4 And that's basically the idea.

Speaker 5 So the whole scientific world was hoping to find the Higgs, except for you, right? You were hoping you wouldn't find it.

Speaker 4 Well, I don't know. This is really important, actually, because

Speaker 4 what is science, right? What you're trying to do is understand nature, which is the real world.

Speaker 4 So if you make a prediction that turns out to be false, then you should be pleased because you've learned more about the world.

Speaker 4 Feynman wrote a beautiful essay called The Value of Science, in which he said that you learn when you do experimental science how to be wrong and how to be pleased.

Speaker 4 Because the moment you're shown to be wrong, you can rule a picture you have about the way that reality works. You can rule it out and you learn something and you move on and you're closer.

Speaker 4 to understanding what's happening or what you observe. So Feynman called science a satisfactory philosophy of ignorance, which I think is a beautiful definition of science.

Speaker 4 The key, if you're an experimental physicist, is to figure out how to make an observation of something in the laboratory or in the real world and make it in such a way that you will be able to learn something about it.

Speaker 4 And that's what you're trying to do.

Speaker 5 I remember having lunch with a guy named Richard Posner. He's a very famous legal scholar in the U.S.

Speaker 5 And he argued emphatically. that there was a non-zero chance that these collisions that were part of the search for the Higgs could create a black hole and destroy humanity.

Speaker 5 Was that complete nonsense? Or did some informed people actually think that might be possible?

Speaker 4 Let's say that you say there is something that happens when particles collide at those energies that is very nasty, whatever it is.

Speaker 4 The answer is that those collisions at those energies are common in the universe. Our particle collider is fine.
It's a kind of high energy thing for us.

Speaker 4 But compared to things like cosmic rays that come flying in and hit the Earth all the time, it's very low energy.

Speaker 4 So you can first of all say, well, we don't observe really weird things happening in particle collisions up there in the sky.

Speaker 4 We're very sure that physics is not unstable in that way, or the universe is not unstable in that way. But you might go further and say, okay, well, fine, but it was a very rare thing.

Speaker 4 So then you can do a calculation and it was done, actually.

Speaker 4 So you say, well, we know how many cosmic rays have hit the Earth over the four and a half billion years that the the earth is here and we know the energy spectrum of them and so we can make a calculation and we can say well given that the earth's still here and hasn't been destroyed in a particle collision from a high energy cosmic ray far in excess of the energies at the large hadron collider then we can put a probability on it let's say there were 10 billion cosmic rays that hit the earth with energies in excess of these energies then you go well there's a one in ten billion chance or something less than that it's not quite that simple but you can put a number on it Upper bound on it.

Speaker 4 In putting an upper bound on it, we've probably made a PR mistake.

Speaker 4 Because, of course, if you're talking about destroying the Earth, then people go, but that means there's a chance.

Speaker 5 We'll be right back with more of my conversation with physicist Brian Cox after this short break.

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Speaker 5 Your most recent book is on black holes. We're talking about black holes.

Speaker 4 I think...

Speaker 5 Like many people, my first real introduction to black holes was Stephen Hawking's book, A Brief History of Time.

Speaker 5 And I think that book must have come out in the 1980s and it sold millions and millions of copies. Probably one of the best-selling science books of all time.

Speaker 5 As you set out to write a book about black holes, did you have that book in the back of your mind?

Speaker 4 Yeah, I mean, it was one of the books that really inspired me when I was thinking about going into physics. And Stephen Hawking is central to the modern story of black hole research.

Speaker 4 The reason Jeff Forshaw and I, my colleague at Manchester, decided to write the book was we became interested in something called the black hole information paradox.

Speaker 4 And I was getting asked about it increasingly in interviews like this, for example. You know, it's not my field.
I'm a particle physicist.

Speaker 4 The study of black holes is partly particle physics, but also it's about general relativity and gravitation.

Speaker 4 And so we thought we would like to learn about some of the really interesting results that are coming out in the context of black holes.

Speaker 4 And just to put it very simply, Stephen in 1974 discovered that one of the things a black hole does is it shakes particles out of the vacuum.

Speaker 4 So there's loads of ideas here, but the vacuum of space is not empty in quantum theory. It's got a rich structure.
And the black hole sort of disrupts that structure.

Speaker 4 What ends up happening is the black hole glows, has a temperature.

Speaker 4 And by the way, if you go to Westminster Abbey and look on Stephen's memorial stone in the Abbey, you'll see his equation for the temperature of a black hole chiseled in stone on the floor of of Westminster Abbey.

Speaker 4 So why is it important? It raised a series of profound questions. And one of them is what happens to stuff that falls into the black hole.

Speaker 4 Because it seemed, according to Stephen's calculation and what we understood at the time, that everything that goes in would be absolutely erased from the universe.

Speaker 4 One of the issues with Stephen's calculation is that if this thing is glowing, this black hole, so it has a temperature, it's emitting particles, then at some point in its life as the universe expands and cools the thing becomes hotter than the universe they're way colder at the moment than the universe but at some point the universe cools down they become hotter so they start losing energy to the universe and essentially they radiate away they disappear they don't have an infinite lifetime these things so that was one of the consequences of stephen's calculation so one day the black hole will be gone all that will be left is the hawking radiation.

Speaker 4 And what Stephen's calculation suggested is that no information is contained in that radiation at all, which is not surprising because the language I used earlier is it's shaken out of the vacuum of space.

Speaker 4 So it's got nothing to do with stuff that falls in. This radiation is coming from the vicinity of the event horizon of the black hole.

Speaker 4 So if an astronaut jumps into the black hole, for example, in Einstein's picture, they just go to the singularity, which is properly thought of as the end of time inside the black hole.

Speaker 4 So they go to the end of time.

Speaker 4 So the question was, it looked like black holes were erasing information from the universe, but the laws of physics that were used to make that statement and make those calculations do not allow for information to be erased.

Speaker 4 They allow for it to be scrambled up, but not erased. So this became known as the black hole information paradox.

Speaker 4 And so that's really the heart of the interest, the theoretical interest in them from the 1980s onwards. Because that's great.

Speaker 4 Going back to what we talked about earlier, the thing that a physicist likes is a paradox. You want your whole theory to collapse, if you can.

Speaker 4 And it did look as if the whole theoretical structure was in danger because of this apparent prediction that black holes destroy information.

Speaker 5 Now, it's interesting to hear you talk as the science communicator, because when we were talking about the Higgs, I don't really understand it, but I can at least pretend like I understand it.

Speaker 5 And I remember when I read Stephen Hawking's book 40 years ago, I don't even think I could pretend to understand it.

Speaker 5 And actually, I've made a conjecture around that book that that is the single most unread book in history.

Speaker 5 Everybody felt like they needed to have a copy of that book in their collection, but regular people just couldn't read it.

Speaker 5 It's interesting because talking about black holes is just categorically difficult to do because I don't think it makes any sense to regular people. So it sounds like a criticism of you.

Speaker 5 You just tried to explain black holes in maybe like a minute, but I will say your book, I actually understood a long ways.

Speaker 5 It gets really hard at the end, but I was with you for about 90% of your book.

Speaker 5 And I want to give you a big compliment for that because you basically covered the same ground as Stephen Hawking and you did it in a way that was really understandable and really exciting.

Speaker 5 It's exciting for someone like me to actually stick with you for 90% of the book.

Speaker 4 Thank you. What you said actually about about the book, probably 90% of it is standard, or 80% of it maybe is standard physics.
A lot of it's general relativity.

Speaker 4 That's Einstein's theory from 1915, his theory of gravity, and gravity as a distortion in space time.

Speaker 4 And that's, I think, quite easy to explain.

Speaker 5 I don't know about that. It's so crazy that time and space are the same thing.
I find that mind-boggling.

Speaker 4 i teach at the university of manchester and i teach special relativity which is the theory from 1905 that einstein published from which e equals mc squared comes we teach that first year first term in a physics degree they're the 18 year olds who are coming to university from school is the first thing we teach them because it's actually mathematically at least easy, but it's conceptually challenging for the reasons that you've said.

Speaker 4 What you see is that basically forced on to the physicists at the time, at the turn of the 20th century, was the idea that space and time are not the way we think they are.

Speaker 4 They're not separate from each other. They're woven together in a sense.
I spoke earlier, moving clocks run slow, our moving rulers shrink, those kind of things.

Speaker 4 But that stuff follows very simply from a single assumption. The The central idea is that the speed of light is a constant.
It's the same for all observers.

Speaker 4 So literally, if you fly towards a source of light, like a flashlight or something, and you fly towards that thing at 99% the speed of light, you will measure the speed of light hitting you in the face to be the speed of light.

Speaker 4 It's just a fixed number.

Speaker 5 Yeah, let me just put it a different way that you put it in the book, because it was maybe the first time it's ever made sense to me. You use the example of cricket, right?

Speaker 5 If you have a cricket bowler that throws the cricket ball 80 miles an hour or something like that, but if you put them on an airplane and they throw it and the airplane's going 300 miles an hour, then when they release that cricket ball, it's going to go 380 miles an hour.

Speaker 5 Okay, and that makes total sense to us.

Speaker 4 But the thing that is completely and utterly bizarre is that now, if you use light and you put something that's going practically the speed of light, and then you throw something at the speed of light it seems like it should be the speed of light plus practically the speed of light all added together but it's only the speed of light that's bizarre yeah and Einstein was the first to take it absolutely literally and say it appears that this is the way that nature is what are the consequences and it's very easy to work out the consequences the hard thing is to accept what we've just said because it's counterintuitive it was strongly suggested by results in electricity and magnetism back in the 1860s, particularly the work of someone called James Clerk Maxwell.

Speaker 4 So it was around this idea for 40 years, I would say. But Einstein did the difficult thing, which is to say, okay, I accept that.
What are the consequences?

Speaker 5 I was surprised to find out reading your book that already in the 1800s, a few people were speculating about black holes. And this was before Einstein.

Speaker 4 And obviously, they didn't get the physics quite right but what kind of arguments were they making I found that really interesting so Laplace who's a very famous French mathematician and also an English clergyman called the Reverend Mitchell it's interesting how often the reverends pop up in old science yeah I think they were people who had space to think so these two apparently independently were thinking about something called escape velocity which is the speed you have to travel from the surface of something to completely escape its gravitational pull.

Speaker 4 So from the Earth, it's about 11 kilometers per second.

Speaker 5 That is so fast. That's seven miles per second.
So the rockets we're shooting, I actually didn't realize we blast those things off. They really are going fast.

Speaker 4 Oh, yeah. You look at the Voyager spacecraft that are heading out as we speak, 50 years after launch.

Speaker 4 into interstellar space, they've achieved escape velocity from the solar system and they're traveling very fast. obviously if you go bigger let's say you go to the sun

Speaker 4 then clearly the gravitational pull at the surface is stronger than it is on the earth's surface turns out the escape velocity is about 620 kilometers per second it's extremely fast so that was known you can calculate that using newton's laws and so what mitchell and laplace thought is well is it possible there are stars and they were thinking of stars that are so massive and they were thinking of enormous stars that the escape velocity at the surface exceeds the speed of light.

Speaker 4 Why not? If such a thing existed, you wouldn't be able to see it because you'd have to go faster than the speed of light to get away.

Speaker 5 Yeah.

Speaker 4 So that's what they were thinking, which is, I think, a really nice idea. And Laplace called them dark stars.
I always remember the quote.

Speaker 4 He said in a paper that he wrote, that the largest objects in the universe may go unseen by reason of their magnitude.

Speaker 5 Now, it's interesting because the thing that they got wrong is actually the black holes that do exist. It's because the huge amount of mass shrinks down to be incredibly small.

Speaker 5 Because when you look at the formula, the closer you are to the center of the thing, the more the gravitation. So they got that piece wrong.

Speaker 4 This is 1790 or something. So they're just thinking, how do you make the gravitational pull really big? Well, you make the thing big, right?

Speaker 4 Perhaps paradoxically at first sight, you can also make the gravitational pull at the surface of something larger by shrinking it. They didn't think of that.
And it's quite radical.

Speaker 4 It turns out that if you take the sun, which is 700,000 kilometers in radius, what's that? 400,000 miles or something, right?

Speaker 4 And you squash it to a radius of three kilometers, so two miles.

Speaker 4 Then you can calculate that the escape velocity at the surface exceeds the speed of light. So that's ridiculous if you think about it.

Speaker 4 You can take the sun, which you can fit a million Earths inside, and squash it down until its radius is three kilometers. Surely that's not going to happen.

Speaker 4 Probably that's why they didn't think of it, because it's ridiculous. That's what you call a black hole, a thing that traps light.
That was realized very early on.

Speaker 4 We're talking about 1920 or so or something like that. But the debate into the 1960s, really was could nature do that to a star?

Speaker 4 So surely you would think if a star runs out of nuclear fuel at the end of its life and collapses, then surely something's going to stop it collapsing down to such a ridiculous state, right?

Speaker 4 But actually, in 1963, Roger Penrose calculated that this will happen for a sufficiently massive star. or anything else actually, just a sufficiently massive thing, no matter what.

Speaker 4 And Roger got the Nobel Prize in 2020 for that paper. So it's not actually that long ago that people were debating these things.

Speaker 4 And if you think about it, it's only the last five or six years that we've really had an image of one, which is from an experiment called the Event Horizon Telescope, which is basically radio telescopes linked together across the face of the Earth.

Speaker 4 An iconic image now of the black hole in the M87 galaxy, which is six billion times the mass of the Sun. It's an astonishing thing, supermassive black hole.

Speaker 4 And now we also have an image of the one in the Milky Way galaxy, which is a bit of a little one, about six million times the mass of the sun-ish. So it's a baby one.

Speaker 5 And so just to play into all the fears that regular people have, so we have this black hole, what's it called, Sagittarius, a star or something like that?

Speaker 4 That's the one in the Milky Way. Yeah.

Speaker 5 And so should regular people worry about that black hole sucking us in in regular time frames?

Speaker 4 That's the thing. They don't suck you in.
If you turn the sun into a black hole, then the planets would carry on orbiting the way that they do now. And that's what happens in the Milky Way.

Speaker 4 And in fact, the Nobel Prize was awarded for looking at the orbits of the stars around the black hole, the Sagittarius A star black hole.

Speaker 4 So there are these stars called the S stars that orbit extremely close to the black hole. Because we can see the orbits, we can infer that there's something extremely dense and extremely small.

Speaker 4 at the center of the Milky Way galaxy. And essentially, the only thing it could be is a black hole.
In order to go into it, you have to fly at it.

Speaker 5 I see.

Speaker 4 It's a deliberate act

Speaker 4 to jump into a black hole.

Speaker 5 So all this starts to make a little bit of sense, but we've talked about already that nothing escapes from black holes.

Speaker 5 But then Stephen Hawking has that famous quote, which is, black holes ain't so black.

Speaker 5 And this now gets into this absurd quantum stuff that I don't think regular people like me have any chance of understanding.

Speaker 4 The only thing I haven't talked about is the event horizon. What is that thing? In Einstein's theory, it's just a region of space.
You could think of it as kind of an imaginary sphere.

Speaker 4 Let's say this is a big, supermassive black hole, a billion times the mass of the sun. Then you can imagine this region of space, which is perfectly spherical if the thing isn't spinning.
And so...

Speaker 4 For a big black hole, you could be sitting there in the room that you're in now, or maybe you're in a car listening to this.

Speaker 4 you could fall in and you wouldn't notice a thing you'd notice nothing you would have crossed though into a region of the universe from which you cannot escape that's what the event horizon is it's the dividing line really so if you're outside the horizon then you can get away with a sufficiently powerful rocket if you're inside you cannot and There are two beautiful ways of thinking about that to my mind.

Speaker 4 One is, which is a bit more abstract, is that you could think of space and time being distorted so much that they essentially swap roles inside the horizon.

Speaker 4 So the singularity, which imagine this big stars collapse, let's say, to form a black hole, you'd probably think of an infinitely dense point sitting there where the star was in space.

Speaker 4 But actually, you should think of this thing as a moment in time. And if you think of it as a moment in time at the center of the black hole, the switch happens happens when you cross the horizon.

Speaker 4 It's like if you say, I want to run away from that thing, I want to get away from it. It's a thing in your future.
It's in your future. So it's like trying to run away from tomorrow, right?

Speaker 4 So that's one way to think about it. The end of time lies inexorably in your future if you cross the horizon.
But the other way, which is maybe more intuitive, is something called the river model.

Speaker 4 It turns out you can rewrite the equations that describe how the black hole forms, more precisely what the black hole is you can rewrite them as a river of space flowing in it's like a sinkhole or your bath where you unplug the plug from your bath and all the water goes down the plug hole right you can rewrite it like that and it turns out that on the horizon the space flows in at the speed of light so that means that if you're something trying to swim out then even if you swim at the speed of light, you're frozen on the horizon because you're trying to swim out at the speed of light and the space is flowing in the river of space at the speed of light so you're stuck there and that's a really beautiful way of looking at it and it goes faster than the speed of light inside so no matter how fast you swim you're going to the plug hole right so that's what the horizon is and stephen hawking calculated that in the vicinity of that thing when you think of quantum mechanics which is what your question is then you find that particles real particles, are emitted from space, basically, and that's the Hawking radiation.

Speaker 4 So, that brings us on to quantum mechanics. And what is it?

Speaker 5 You're listening to People I Mostly Admire. I'm Steve Levitt, and after this short break, physicist Brian Cox and I will return to talk about his time as a pop star.

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Speaker 5 Before Brian was a physicist, he had a moment as a pop star. His first big break was in a band called Dare that was founded by one of the members of Thin Lizzy.

Speaker 5 The name Thin Lizzy probably doesn't mean much to my younger listeners, but to some of my generation, Thin Lizzy was a big deal.

Speaker 5 I asked Brian how he managed to finagle his way into a band with a member of Thin Lizzie.

Speaker 4 It was luck. I got interested in music, just as everyone does when you're a teenager.
And so I learned to play, not really very well, but I taught myself to play keyboards.

Speaker 4 And I made a demo tape when I was 16 with a band I was in.

Speaker 4 And Darren Wharton, who was a keyboard player from Thin Lizzy, had moved in close to where I lived in Oldham, near Manchester, for some reason. I don't know why.

Speaker 4 And he used to go in the pub with my dad. And my dad took him the demo tape.
And then when Lizzie split up, he formed a band in Oldham.

Speaker 4 And he remembered that there was a guy who played keyboards up the road. And he asked me to go down and audition.

Speaker 4 I wasn't a very good keyboard player, but what I was good at, and this probably is not surprising given my future career, is I was good at the tech stuff.

Speaker 4 So I could take these keyboards and these old synthesizers, as they were, we're talking mid to late 80s now. It was all a bit complicated, and I could make them work.

Speaker 4 I think he recognized that and thought, well, there's a guy here, he looks okay, and he can plug wires in. He understands MIDI and all that kind of stuff.
So he's good. So I got in the band.

Speaker 4 So I took a year off university and I did, we call it a gap year in the UK.

Speaker 4 And in that time, the band got a record deal. with AM Records.
And so when I was supposed to be at university, I found myself ultimately in Los Angeles recording an album.

Speaker 4 And I'd only been out of the country once.

Speaker 4 And suddenly I'm in LA recording an album at Joni Mitchell's house with Larry Klein, who's still a great producer, Larry, and he was married to Joni at the time.

Speaker 4 So we made the album, an album called Out of the Silence, which I still like, by the way. I think it's a really good late 80s kind of soft rock album.

Speaker 4 Then they called us up, A ⁇ M, and said, okay, you're going to make a video for the song? And then they said, oh, you're touring now. You're going to support Jimmy Page.

Speaker 4 And then ultimately, we ended up supporting Europe, the band Europe had a big hit, the final countdown. Oh, yeah, right.
Yeah. In North America.

Speaker 4 It was just bizarre that I went from this guy, you know, who was basically going to do some physics or something at university to recording albums in Joni Mitchell's studio and touring with Jimmy Page.

Speaker 5 Was the touring the kind of rock and roll debauchery that we associate with the 1980s?

Speaker 4 Yeah, we had a good time. We were late teens, early 20s, a band from Oldham, just kids from North Manchester, who had no sort of interaction with that world at all.

Speaker 4 And it was a wonderful thing to do, as you can imagine. So I made two albums, toured a lot, then basically had a fight in a bar in Berlin.
as you do. The band actually didn't split up.

Speaker 4 It's actually still going. But I left and the guitarist left and I went to do physics at university.

Speaker 5 Okay, so you say that, but even crazier is you then joined this band D-Reem in 1993, just in time for this incredible song.

Speaker 5 It's called Things Can Only Get Better, and it's a number one hit for four weeks in 1994. I mean, that's just so crazy.

Speaker 4 Lucky, again, we had the fight in the bar in, I think it was October. And that's optimally bad if you want to go to university because university starts in September.
You've got to wait a year to go.

Speaker 4 So in the intervening year, I needed a job and I got a job as a sound engineer and sort of a tour manager. And one of the bands was DeReem, who didn't have a record deal.

Speaker 4 And then they got a place on a TV show, a local TV show in London, and they didn't have a keyboard player. So they said to me, well, you know how to play keyboards, don't you? And you look look okay.

Speaker 4 So will you just stand there and play the keyboard? So I did that and accidentally joined the band. And as you rightly say, then that album ultimately became a really big album.

Speaker 4 And we toured with bands like Take That. We had some big tours and ended up on this show called Top of the Pops in the UK, which is the show that everybody grows up with and wants to be on.

Speaker 4 And so, yeah, I did it again by accident when I was at university.

Speaker 5 And then crazier than anything, this is the song that then gets adopted by the Labour Party and is played all the time. It's like part of Tony Blair's celebration, right? Yep.

Speaker 4 97, a very famous election in the UK. And the Labour Party asked us if they could use the song, things suddenly get better.
And we said yes.

Speaker 4 At that time, I think Tony Blair was the most popular politician you could imagine. And he was definitely going to become prime minister.
And everybody basically voted for Labour.

Speaker 4 It became iconic, this song. And it actually came back because we had an election last year in the UK.
And it was a similar feel. It didn't quite work out that way with the optimism.

Speaker 4 But at the time, there was a sense of change. And so the single went back into the charts again last year.
Every time there's a real election that signifies change and optimism, that song comes back.

Speaker 4 And we ended up getting the band back together and playing at Glastonbury. Oh, my gosh.
So I could never quite escape music, but I love it.

Speaker 5 Tell me about your upcoming world tour called Emergence. What's that?

Speaker 4 Yeah, so it started with giving public lectures in physics and they got more popular.

Speaker 4 And I started to think more about how I could broaden the audience because I've always said that science is too important not to be part of popular culture and I really mean it.

Speaker 4 And so the opportunity came up to put that into practice and do some bigger shows. And they've ended up very big.
And so in the UK now, they're arena shows.

Speaker 4 So they go to 15 000 people and then you really have to think about what you do so you start using enormous led screens and you start commissioning graphics and also the images from things like the james webb space telescope vera rubin observatory all this are so high resolution that you can put them i think the screens are a hundred feet across in the arenas

Speaker 4 and so that tour emergence, I'm writing it now and we begin to do it next year. And I was inspired by Kepler, so Johannes Kepler, he's most famous for the laws of planetary motion.

Speaker 4 He figured out, astonishingly, to my mind, that planets orbit around the sun in ellipses and there's a relationship between the year, the period of the orbit, and the distance from the sun.

Speaker 4 Kepler wrote this book called The Six-Cornered Snowflake in 1610.

Speaker 4 which was about him walking across the Charles Bridge in Prague in a snowstorm and seeing snowflakes land on his arm and trying to understand why they're all six-sided.

Speaker 4 There's a wonderful quote from him where he says, this can't be by chance. There's got to be a reason.
And it's a very modern way of thinking actually.

Speaker 4 We started our chat by talking about the standard model and the Higgs boson. And I probably mentioned symmetries of mathematical equations.

Speaker 4 So regularities, they're what ultimately led to the standard model.

Speaker 4 Now, Kepler noticed there's a symmetry, which is this six-fold symmetry of a snowflake, and correctly thought, well, that's something about the underlying reason for these things.

Speaker 4 Now, but it's a 20th century discovery. We know that's because of the shape of the water molecule.
And why is the shape of the water molecule the way that it is? Because of quantum mechanics.

Speaker 4 And so we can do it all, but it's the 20th century. So I got fascinated by this mind that in 1600, that's a modern mind, he's a true genius.

Speaker 4 But also, it's only 400 years ago it's the birth of modern science same 400 years roughly speaking we're the same time as galileo shortly after copernicus so we're at the birth of modern science i was just think if you'd have taken an ancient egyptian from says 3000 bc and you'd brought them forward in time to ancient rome around zero a d 3 000 years they wouldn't have been too surprised.

Speaker 4 There's not a lot of change. So what is it about the way of thinking that those people and others discovered around that time that's catapulted us outside of our solar system in just a few centuries?

Speaker 4 All those worlds that Kepler saw as points of light in the sky, we visited them all. Mars, which was central to this, the laws of planetary motion, to understanding them, we've got rovers on it.

Speaker 4 We're searching for life on the surface now. We have spacecraft heading out of the solar system, 400 years.
And so, there's a question: why?

Speaker 4 What is this thing we call science, this way of thinking and interrogating nature that's taken us from the end of the medieval period and onwards to the enlightenment and then to the stars basically in 400 years?

Speaker 4 And also, what we might become if we can continue that exploration of nature and all the things that we've talked about, and we don't let superstition and darkness re-enter the world.

Speaker 5 Brian Cox's most recent book is titled Black Holes: The Key to Understanding the Universe. For more information about the Brian Cox Emergence Tour, check out the website briancoxlive.co.uk.

Speaker 5 That's B-R-I-A-N-C-O-X-L-I-V-E dot CO.uk.

Speaker 5 So this is a point of the show where I welcome on my producer producer Morgan to handle a listener question.

Speaker 9 Hi, Steve. So we have a question from a listener named Nick.
Nick asks, why isn't there a requirement for gun liability insurance? It works reasonably well for cars.

Speaker 9 He thinks that liability insurance for guns would be a good mechanism to regulate the costs guns impose on society since direct government regulation doesn't garner enough political will.

Speaker 9 What do you think of this idea?

Speaker 5 So let's start with the underlying problem, which is that guns have a negative externality. And that's just economics jargon for when something I do imposes costs on other people.

Speaker 5 And there is a standard economic solution to deal with externalities, and it's to impose a tax, right?

Speaker 5 If you can figure out how much burden an activity imposes on others, and then you levy a tax of that amount, it turns out after you work through the math that it leads to an efficient solution.

Speaker 5 So the most straightforward thing to do would be to impose a tax on guns. What Nick is saying though is, oh, that's not politically viable.

Speaker 5 Maybe insurance, liability insurance, would be a way to get political support for this idea. I'll be honest with you, it's not an idea I've ever pondered before.

Speaker 5 And so what Nick is saying is when I own a car, I'm required to hold third-party insurance.

Speaker 5 So I don't have to have car insurance that covers my own collision damages, but I do have to have car insurance. So if someone else else gets hurt in a crash that I cause, then I'm liable for that.

Speaker 5 And the idea is maybe you could do the same with guns. And at first blush, this seems like a reasonable idea, but I have to say, the longer I've thought about it, the less I like it.

Speaker 9 Really?

Speaker 5 So first of all, you start with a big problem that there are already laws in place that shield gun manufacturers and gun dealers from liability. Maybe those laws shouldn't be there, but they are.

Speaker 5 So if if you want to think about imposing insurance, you're really talking about putting the burden on the gun owners.

Speaker 5 And once you start looking at the data, things really start to unravel because gun deaths take three forms, suicide, homicide, and accidents. And by far, suicide is the biggest number.

Speaker 5 Maybe 27,000 people per year in the U.S. are using guns to commit suicide.
Clearly, liability insurance doesn't make any sense here at all. There's no third party to compensate.

Speaker 5 So this isn't dealing at all with the biggest source of gun deaths.

Speaker 5 The second way in which people die with guns is homicide. And there's roughly 15,000 gun homicides per year in the U.S.
But there's two problems when you think about insurance.

Speaker 5 First of all, the majority of gun homicides are done with illegal guns. And one thing you can be sure of is that illegal gun owners will not be getting this insurance.

Speaker 5 So I just don't think it really solves the bulk of the problem related to homicides.

Speaker 9 But wait, and I don't have any data on this, but I feel like with school shootings, which we hear about in the news, often kids, high schoolers are taking their parents'

Speaker 9 legally purchased gun and bringing it to school and shooting classmates, teachers, people on campus.

Speaker 5 While it is true that a lot of attention is given to school shootings, and for good reason, the actual numbers relative to overall homicide is small.

Speaker 5 I think historically, if you looked at the numbers, we're talking about 30, 40 deaths per year.

Speaker 5 And obviously, that's 30 or 40 deaths per year too much, but it's really a drop in the bucket compared to the 15,000 homicides.

Speaker 5 So I think if you think about the machinery you would have to put around trying to do this, and it's probably politically infeasible anyway, it really, in the end, there've got to be better ways to compensate the victims of gun deaths than this.

Speaker 5 And I think it's very unlikely that any any school shooter's behavior would be changed because of the existence of this insurance.

Speaker 5 I think far more important potentially in terms of numbers would be accidental gun deaths. And looking at the data there, there are about 500 accidental gun deaths a year.

Speaker 5 And many of those, I imagine, are with legal guns. But the thing is, when you look at the data, about 90% of accidental deaths are of friends and family.

Speaker 5 So again, you don't really have this innocent third party unrelated to you that needs to be compensated for the mistake.

Speaker 5 So in the end, what's ironic about this is that if you actually had this insurance and the insurance were there to compensate third parties who were strangers to you for legal gun ownership, I think the result would be that the insurance premiums would be really low because the actual risks that come from legal gun owners to strangers turn out to be really low.

Speaker 9 So you really don't think that requiring gun liability insurance is a good policy?

Speaker 5 I don't, but I have to say that thinking through it was a really valuable exercise for me and it clarified my thinking in all sorts of ways.

Speaker 9 Nick, thank you for such an interesting question. Listeners, if you have a question for Steve Levitt or a problem that could use an economic solution, send us an email.

Speaker 9 The show's email address is pima at freakinomics.com. That's P-I-M-A at freakonomics.com.
We read every email that's sent and we look forward to reading yours.

Speaker 5 Next week, we've got an encore presentation of my conversation with best-selling author Surleika Jawad.

Speaker 5 And in two weeks, it's a brand new episode featuring my friend and colleague, economist Michael Greenstone. He's doing economic research that is more

Speaker 5 and policy relevant than just about anybody else I know. As always, thanks for listening and we'll see you back soon.

Speaker 6 People I Mostly Admire is part of the Freakonomics Radio Network, which also includes Freakonomics Radio and the Economics of Everyday Things. All our shows are produced by Stitcher and Renbud Radio.

Speaker 6 This episode was produced by Morgan Levy and mixed by Jasmine Klinger. We had research assistance from Daniel Moritz-Rabson.
Our theme music was composed by Luis Guerra.

Speaker 6 We can be reached at pima at freakonomics.com.

Speaker 4 That's p-im-a at freakonomics.com. Thanks for listening.

Speaker 4 I'm sorry that I have everything in kilometers, right?

Speaker 5 The fact that Americans still don't know kilometers 50 years after the rest of the world changes like a sad state, man. We should be punished for that.

Speaker 2 The Freakonomics Radio Network, the hidden side of everything.

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